Add detachFromTarget call when closing session

- Modified open_session() to call detachFromTarget in a finally block
- Added tests to verify detachFromTarget is called on normal exit and exception

Co-authored-by: P4X-ng <223870169+P4X-ng@users.noreply.github.com>

Author: Copilot

tests/test_session_detach.py

@@ -0,0 +1,130 @@
+"""
+Test that detachFromTarget is called when closing a session.
+"""
+import json
+import logging
+import sys
+import os
+
+# Add the source directory to path
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..'))
+
+from cdp import target
+import pytest
+import trio
+from trio_websocket import serve_websocket
+
+# Import directly from the main module to avoid generated imports
+from trio_cdp import CdpConnection, open_cdp
+
+# Import test utilities
+from . import fail_after
+
+
+HOST = '127.0.0.1'
+
+
+async def start_server(nursery, handler):
+    ''' A helper that starts a WebSocket server and runs ``handler`` for each
+    connection. Returns the server URL. '''
+    server = await nursery.start(serve_websocket, handler, HOST, 0, None)
+    return f'ws://{HOST}:{server.port}/devtools/browser/uuid'
+
+
+@fail_after(5)
+async def test_session_detach_on_exit(nursery):
+    """Test that detachFromTarget is called when exiting open_session context."""
+    detach_called = False
+    
+    async def handler(request):
+        nonlocal detach_called
+        try:
+            ws = await request.accept()
+            
+            # Handle "attachToTarget" command
+            command = json.loads(await ws.get_message())
+            assert command['method'] == 'Target.attachToTarget'
+            assert command['params']['targetId'] == 'target1'
+            logging.info('Server received attachToTarget: %r', command)
+            response = {
+                'id': command['id'],
+                'result': {
+                    'sessionId': 'session1',
+                }
+            }
+            logging.info('Server sending: %r', response)
+            await ws.send_message(json.dumps(response))
+            
+            # Handle "detachFromTarget" command
+            command = json.loads(await ws.get_message())
+            assert command['method'] == 'Target.detachFromTarget'
+            assert command['params']['sessionId'] == 'session1'
+            detach_called = True
+            logging.info('Server received detachFromTarget: %r', command)
+            response = {
+                'id': command['id'],
+                'result': {}
+            }
+            logging.info('Server sending: %r', response)
+            await ws.send_message(json.dumps(response))
+        except Exception:
+            logging.exception('Server exception')
+    
+    server = await start_server(nursery, handler)
+    
+    async with open_cdp(server) as conn:
+        async with conn.open_session(target.TargetID('target1')) as session:
+            assert session.session_id == 'session1'
+            # Don't do anything else in the session
+    
+    # After exiting the session context, detach should have been called
+    assert detach_called, "detachFromTarget was not called when session closed"
+
+
+@fail_after(5)
+async def test_session_detach_on_exception(nursery):
+    """Test that detachFromTarget is called even when an exception occurs in the session."""
+    detach_called = False
+    
+    async def handler(request):
+        nonlocal detach_called
+        try:
+            ws = await request.accept()
+            
+            # Handle "attachToTarget" command
+            command = json.loads(await ws.get_message())
+            assert command['method'] == 'Target.attachToTarget'
+            logging.info('Server received attachToTarget: %r', command)
+            response = {
+                'id': command['id'],
+                'result': {
+                    'sessionId': 'session1',
+                }
+            }
+            await ws.send_message(json.dumps(response))
+            
+            # Handle "detachFromTarget" command
+            command = json.loads(await ws.get_message())
+            assert command['method'] == 'Target.detachFromTarget'
+            assert command['params']['sessionId'] == 'session1'
+            detach_called = True
+            logging.info('Server received detachFromTarget: %r', command)
+            response = {
+                'id': command['id'],
+                'result': {}
+            }
+            await ws.send_message(json.dumps(response))
+        except Exception:
+            logging.exception('Server exception')
+    
+    server = await start_server(nursery, handler)
+    
+    async with open_cdp(server) as conn:
+        with pytest.raises(RuntimeError):
+            async with conn.open_session(target.TargetID('target1')) as session:
+                assert session.session_id == 'session1'
+                # Raise an exception in the session
+                raise RuntimeError("Test exception")
+    
+    # After exiting the session context, detach should still have been called
+    assert detach_called, "detachFromTarget was not called when session closed with exception"

trio_cdp/__init__.py

@@ -239,8 +239,12 @@ async def open_session(self, target_id: cdp.target.TargetID) -> \
         and it will execute on the current session automatically.
         '''
         session = await self.connect_session(target_id)
-        with session_context(session):
-            yield session
+        try:
+            with session_context(session):
+                yield session
+        finally:
+            await self.execute(cdp.target.detach_from_target(
+                session.session_id, session.target_id))
 
     async def connect_session(self, target_id: cdp.target.TargetID) -> 'CdpSession':
         '''